Date: Mon, 21 Aug 2023 08:19:28 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Mateusz Guzik <mjguzik@gmail.com>, current@freebsd.org Subject: Re: Speed improvements in ZFS Message-ID: <58ac6211235c52d744666e8ae2ec7568@Leidinger.net> In-Reply-To: <ZOKC3-6uyPUO8qNY@kib.kiev.ua> References: <CAGudoHG5Fgg4184SsXhzqYRR7VPaBXZoirGvyRyJX5ihX5YG-A@mail.gmail.com> <ed1f82dd26d3cc9ec9cc16505109ec40@Leidinger.net> <CAGudoHEP8TrSzz0TL-PsOx0WNc7z3042wJk-jhhVwhTyJ0VEQQ@mail.gmail.com> <88e837aeb5a65c1f001de2077fb7bcbd@Leidinger.net> <4d60bd12b482e020fd4b186a9ec1a250@Leidinger.net> <CAGudoHE7RPcHpQEqKbzRM8cJcYKue17=iPVv8iOfZq03h22tTA@mail.gmail.com> <73f7c9d3db8f117deb077fb17b1e352a@Leidinger.net> <CAGudoHGPw0Dmnv6ont8JGyLsT7qv%2BQqAFZO3tKOpNo3eN%2BJgLQ@mail.gmail.com> <58493b568dbe9fb52cc55de86e01f5e2@Leidinger.net> <CAGudoHEyZh1DU=j_6mOfB3tSKhC-pNokPgONDbf4oF3D3A5=jg@mail.gmail.com> <ZOKC3-6uyPUO8qNY@kib.kiev.ua>
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Am 2023-08-20 23:17, schrieb Konstantin Belousov: > On Sun, Aug 20, 2023 at 11:07:08PM +0200, Mateusz Guzik wrote: >> On 8/20/23, Alexander Leidinger <Alexander@leidinger.net> wrote: >> > Am 2023-08-20 22:02, schrieb Mateusz Guzik: >> >> On 8/20/23, Alexander Leidinger <Alexander@leidinger.net> wrote: >> >>> Am 2023-08-20 19:10, schrieb Mateusz Guzik: >> >>>> On 8/18/23, Alexander Leidinger <Alexander@leidinger.net> wrote: >> >>> >> >>>>> I have a 51MB text file, compressed to about 1MB. Are you interested >> >>>>> to >> >>>>> get it? >> >>>>> >> >>>> >> >>>> Your problem is not the vnode limit, but nullfs. >> >>>> >> >>>> https://people.freebsd.org/~mjg/netchild-periodic-find.svg >> >>> >> >>> 122 nullfs mounts on this system. And every jail I setup has several >> >>> null mounts. One basesystem mounted into every jail, and then shared >> >>> ports (packages/distfiles/ccache) across all of them. >> >>> >> >>>> First, some of the contention is notorious VI_LOCK in order to do >> >>>> anything. >> >>>> >> >>>> But more importantly the mind-boggling off-cpu time comes from >> >>>> exclusive locking which should not be there to begin with -- as in >> >>>> that xlock in stat should be a slock. >> >>>> >> >>>> Maybe I'm going to look into it later. >> >>> >> >>> That would be fantastic. >> >>> >> >> >> >> I did a quick test, things are shared locked as expected. >> >> >> >> However, I found the following: >> >> if ((xmp->nullm_flags & NULLM_CACHE) != 0) { >> >> mp->mnt_kern_flag |= >> >> lowerrootvp->v_mount->mnt_kern_flag & >> >> (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED | >> >> MNTK_EXTENDED_SHARED); >> >> } >> >> >> >> are you using the "nocache" option? it has a side effect of xlocking >> > >> > I use noatime, noexec, nosuid, nfsv4acls. I do NOT use nocache. >> > >> >> If you don't have "nocache" on null mounts, then I don't see how this >> could happen. > > There is also MNTK_NULL_NOCACHE on lower fs, which is currently set for > fuse and nfs at least. 11 of those 122 nullfs mounts are ZFS datasets which are also NFS exported. 6 of those nullfs mounts are also exported via Samba. The NFS exports shouldn't be needed anymore, I will remove them. Shouldn't this implicit nocache propagate to the mount of the upper fs to give the user feedback about the effective state? Bye, Alexander. -- http://www.Leidinger.net Alexander@Leidinger.net: PGP 0x8F31830F9F2772BF http://www.FreeBSD.org netchild@FreeBSD.org : PGP 0x8F31830F9F2772BF
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